'Normal' nuchal translucency: a justification to refrain from detailed scan? Analysis of 6858 cases with special...

To assess the prevalence and detection rate of major anomalies (MAs) by applying first trimester anomaly scan (FTAS) including first trimester fetal echocardiography (FTFE) to all fetuses and discuss ethical implications.

The study group included 6879 consecutive fetuses with known outcome of pregnancy (follow-up: 98%), 6565 with 'normal' nuchal translucency (NT) (≤ P95), 314 with 'increased' NT (> P95). All fetuses received FTAS/FTFE. As MAs with the potential of being detected at FTAS/FTFE, we defined anomalies present at conception or developed during first trimester.

Prevalence of MAs in fetuses with 'normal' NT reached 1.7%. Although 29.8% of chromosomal abnormalities were found in the group of 'normal' NT, 77% of MAs accompanied by a normal karyotype were found in this group. In fetuses with 'normal' NT and MA, diagnosis was made prenatally in 87.4% (FTAS/FTFE: 58.6%).

A relevant number of MA is present in fetuses with 'normal' NT. More than half will be detected by FTAS/FTFE. As consequence, one should discuss a concept in which also in fetuses with 'normal' NT, FTAS/FTFE should be offered. This concept can also be justified from an ethical point of view, which focuses on the principles of nonmaleficence, justice and respect for autonomy of the pregnant woman.